1. The Field of the Invention
The present invention relates generally to optical transceiver modules employed in optical communications networks. More specifically, the present invention relates to an adjustable optical transceiver design that maximizes thermal dissipation from heat-sensitive transceiver components.
2. Background and Relevant Art
Fiber optic technology is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing fiber optic technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission.
Optical communications networks employ optical transceivers in transmitting information via the network from a transmission node to a reception node. FIGS. 1A, 1B, and 2A through 2B illustrate conventional configurations of an optical transceiver 100, which includes a frame, a housing 110, and an optical sub assembly (e.g., Transmit Optical Sub-Assembly 150) used to transmit or receive optical information. In particular, a Transmit Optical Sub-Assembly (“TOSA”) 150 at the transmission node of an optical network receives an electrical signal from an electronic device, such as a computer, and converts the electrical signal into a corresponding optical signal. The TOSA 150 then transmits the optical signal over a fiber optic cable to a reception node of the network.
The transceiver 100 can also serve as a reception node on the optical network. In particular, the conventional transceiver 100 includes a Receive Optical Sub-Assembly (“ROSA”) component 155 (FIG. 2A), which receives the optical signal over the optical fiber, and uses, for example, a photodetector to convert the optical signal into corresponding electrical signals. The electrical signals are then forwarded to a host device, such as a computer, for processing.
Generally, a conventional “OSA”, a generic term for the TOSA 150 or ROSA 155, includes a main body 183, a nose piece 170, and, in some cases, an alignment ridge 180 that aids the OSA physical alignment within the transceiver module 100. A conventional transceiver 100 includes an outer housing 110 having inner walls 130, 140, and an alignment ridge 120 that can be used to position the OSAs via, for example, portion 180. The conventional transceiver walls 130, 140 surround one or more internal cavities, which serve as one or more fiber optic receptacles for conventional “LC” or “SC” optical connector ends. Mounted inside an assembled transceiver module 100 generally, therefore, are the TOSA 150, ROSA 155, and a transceiver substrate (e.g., a printed circuit board) 125. The TOSA 150 and ROSA 155 are connected to the transceiver substrate 125 via any number of connectors, such as the illustrated flex connectors 165.
Since OSA performance, in particular TOSA performance, can be affected adversely by excessive temperatures, it is important in some cases to provide adequate, reliable means to remove the heat from the TOSA and from the transceiver, generally. One way in which this is typically done with cylindrical TOSAs (e.g., 150) is with a thermally conductive extension 160, which conducts heat from the inner core of the TOSA 150 onto a separate heat dissipating element 105. The heat dissipating element 105 in turn distributes the heat outside of the transceiver module 100. In contrast with cylindrical TOSAs 150, a box-shaped OSAs (not shown) disperses heat directly to the transceiver housing 110 due to surface-to-surface contact, and hence without a separate heat dispersion tongue 160.
Unfortunately, some challenges arise in providing adequate TOSA heat dissipation, based at least in part on alignment procedures inherent in the manufacturing process. For example, the TOSA front end 170 (as well as the ROSA front end) is typically aligned as a separate component to the TOSA body 183, prior to mounting the TOSA 150 to a transceiver package. Any variability, however slight, that is introduced when aligning the TOSA front end 170 to the back end 183 can make it difficult to both conduct heat out of the TOSA and at the same time ensure that the TOSA 150 and ROSA 155 are both properly aligned for a given optical cable connector interface.
In particular, this variability between a TOSA and ROSA in the transceiver module can pose a particular challenge for using conventional heat dissipating components (e.g., 105). Generally speaking, if heat dissipating components were composed of substantially flexible materials, there would be less difficulty in aligning and fitting a given TOSA in a transceiver assembly in n appropriate position relative to the ROSA. In particular, a flexible heat dissipating component could be made somewhat larger than required, and then compressed to the appropriate fit, to ensure the TOSA and ROSA front ends are aligned with similar X and Y positioning inside the transceiver housing. Flexible materials, however, are not good thermal conductors, and therefore poor heat dissipaters.
On the other hand, rigid heat dissipating elements create other difficulties related to whether the TOSA and ROSA in a transceiver can be coupled with a conventional optical fiber connector interface. In short, when aligning the relevant OSA (TOSA or ROSA) front end to its respective back end, the OSA front end is often slightly offset relative to its respective OSA body by a measure of thousandths of an inch. With conventional OSAs that do not require heat dissipation, this is not ordinarily a very big problem since the front ends of each OSA are still secured (e.g., by alignment ridge 120 on the transceiver frame, and alignment ridge 180 on the OSA) in a uniform spatial position in the transceiver housing 110. In particular, transceivers that do not require heat dissipation also allow the respective back ends of the TOSA and ROSA to vary with respect to each other. For example, the respective back ends of the TOSA and ROSA are typically connected to the transceiver substrate 125 with some sort of flexible connector, such as the illustrated flex circuit 165, which accommodates the back end variation.
Unfortunately, when using a rigid heat dissipation element (e.g., 105), the TOSA 150 back end can not be allowed to float freely. In particular, the TOSA 150 that implements heat dissipation also has its back end (e.g., 183, and conductive tongue 160) secured to the rigid heat dissipation element 105. This securing of the OSA back end can cause a corresponding, slightly-offset spatial position of the TOSA front end 170 relative to the ROSA 155 front end 175 position inside the transceiver housing 110, due to the previously described OSA alignment variations.
In many cases, this offset spatial position of the TOSA front end 170 is different enough from the spatial position of the ROSA front end 175 inside the transceiver housing 110 that the TOSA front end 170 and ROSA front end 175 do not adequately align with a conventional optical fiber connector. In particular, differences of thousandths of an inch in OSA alignment can cause significant stress on the transceiver when trying to get rigidly mounted parts to fit in a defined optical connector space. Such seemingly miniscule differences, which are amplified in small form factor components, can also cause failure of the optical cable to connect to the transceiver in the first instance.
Accordingly, an advantage in the art can be realized with optical transceivers that can dissipate heat more reliably in systems such as small form factor systems. In particular, an advantage can be realized with heat dispersion systems that dissipate heat efficiently in an optical transceiver, without significantly complicating important positioning between a TOSA and ROSA, such that the TOSA and ROSA can still readily connect to a standardized optical fiber connector.